Infrared thermal measurement and thermal imaging are widely used for predictive and preventative maintenance operations because of their ability to image lost energy which may result from poor electrical connections, mechanical friction, electrical or mechanical overloads, or other failing components.
In many cases, thermographic inspections are done regularly on electrical and mechanical equipment within a building or plant. The resulting data is reviewed for obvious problems (hot spots) which indicate imminent failure. In addition, the data may be compared to an established baseline, or trended over time to look for early warning signs. Such trend-based results may enable changes which prevent a failure altogether, or allow changes at the next scheduled maintenance.
In other cases, many different items of the same or similar type are thermographically screened over time, as might be the case with electrical/mechanical equipment production, engine maintenance in fleets, or field service of heavy equipment. In this case again, obvious hot spots may be easily identified, but more subtle anomalies must be identified with baseline data from a “known good” product, or using trend data from repetitive visits to the equipment in question.
Some companies offer thermal infrared inspection tools which include visible cameras. For instance, the Fluke 576 data-logging infrared spot thermometer is identical to the Fluke 574 data-logging spot thermometer except for the addition of a visible camera, for an additional $700 or more (at retail). Both of these instruments are suitable for repeated inspection of equipment within a plant, or of many identical pieces of equipment (hence the data-logging function). In addition this product—as almost any infrared spot thermometer does—includes a laser designator corresponding to the spot being measured. For the purpose of alignment, the user is advised to print a photo showing the laser spot(s) and then use it as a reference for future inspections. Besides the impracticality of carrying a large book of photos around a plant, the position of a laser spot on the object of interest does not uniquely determine sensor position vis-à-vis the object, causing potential discrepancies between measurements.
Similarly, thermal infrared inspection cameras are offered with the option to add visible imaging to enable “fusion” displays in real-time, and offline reporting—typically at costs of thousands of additional dollars. However, no alignment tools have been integrated into these cameras, and users must still resort to looking back and forth to the baseline image (on a piece of paper). As a result, the effectiveness of these inspection tools—often upwards of $10,000 in price—is dramatically limited because no current-vs.-baseline or trending analysis can be done in the field, and such trend analysis is complex and time-consuming even after the infrared image data has been loaded onto a PC for off-line analysis (because often a human must manually match new images with the baseline). This limits the applicability of these products to expert users leaving a large reserve of technicians underutilized.